Maritime salvage equipment



March 12, 1963 G. w. LEHMANN 3,080,844

MARITIME SALVAGE EQUIPMENT Filed May 29, 1959 4 Sheets-Sheet 1 Mrs 1 01? GOG/V7710? M LEI/M4 10 WA MH.W

AGE/Yr March 12, 1963 G. w. LEHMANN 3,080,844

MARITIME SALVAGE EQUIPMENT Filed May 29, 1959 4 Sheets-Sheet 2 Gosh/ruse M Lawn/Y4 MAMW AGE/Yr March 12, 1963 G. w. LEHMANN 3,030,844

MARITIME SALVAGE EQUIPMENT Filed May 29, 1959 4 Sheets-Sheet a FIG. 7

In va me Gus/17146. M LEI/MANN AGE/Yr March 12, 1963 s. w. LEHMANN MARITIME SALVAGE EQUIPMENT 4 Sheets-Sheet 4 Filed May 29, 1959 FIG. 9

FIG. 70

United States Patent s Claims. c ne-s41" Thepresent invention relates to improvements in devices for effecting maritime salvage work and. more. particularly tofie'xibl'e and folda-blesalvage bags which may be inflated. to become buoyant bodies.

'Maritime salvage. work usuallyis performed byropes attached to awrec'k. After the ropes are set tight to a Wreck, ballast compartments of. the salvage barge. are drained. and. the. wreck israised. This. method often requires several strokes fonraising a wreck to thesurface, whereupon leaks are patched to get the wreck fully. and independently afloat. Smaller salvage jobs are dcne'by merely using. ropes to pull a wreck to the surface Without using the lifting power of a salvage bargev by draining her ballast compartments. In othercases, damaged compartments are drained after leaks have been patchedin order to raise, a, ship. Further methods providebuoyancy bodies, preferably cylindrical or spherical steel containers or pontoons, which are submerged by ballast water and then attached to awreck. Draining, or pressing the water ballast out. of the containers by air provides the required lifting force to raise a wreck to the, surface.

Inasmuch as such steel containers or pontoons require a considerable stowagespace on board a salvage barge or expensive towing, sometimes over long sea distances, which is particularly expensive, in case of a. great number of containers for large salvage jobs and, furthermore, in consideration of the heavy weight of such containers it is, one object of the present invention to provide buoyancy bodies for salvage purposes which are constructed of foldable bags, preferably of plastic material and in par.- ticular of nylon.

Other objects of the present invention and advantageous features thereof will become apparent as the description proceeds.

As described hereunder, the proposed bags are, sub.- merged in folded condition to the proper location at the wreck. Upon attaching the bags to the wreck, they are inflated by compressed air or gas-evolving chemical substances, thus causing the bags to expand and, consequently, buoyancy forces are developed which lift the attached wreck to the surface. It is desirable to equip the salvage bags with a pressure differential valve to keep the air or gas pressure inside the bags at a constant level while the bags are, rising to lower water levels where less water pressure is present. According to the present invention the pressure differential valve. is preferably adjusted in such a way that a small excess pressure is always maintained inside thejbag against the outer water pressure. In this nianner, the circumference stress of the bag at different levels remains constant at any water depth and at a low rate, The bag is kept upright during expansion at changing inside and outside pressures, thus providing maximum possible buoyancy throughout the entire raising procedure notwithstanding the water depth.

l The invention w ill be more fully described in the following description of certain prefer-red embodiments thereof, as shown in the accompanying drawing, without, however, being in any way limited to the illustrated BAX- atnples. the drawing, X

3,080,844 Patented Mar. 12, 1963 FIGURE. 1. shows a cross. section through an inflated salvage. bag;

FIGURE. 2. shows. attachment means for the flexible fabricofthe bagto the rigid. bottom and top members, illustrated. inconnection with. the. top member;

FIGURE 3 shows' section along lineIII+IH of FIG- FIGURE. 4 showsna. salvagebagin folded condition. attached to. an outriggef'which, inthrn, 'is attached toithe wreck; i i

FIGURE 5.- shows one example of,a screw and, bolt connection of a. footplate of, an outrigger to the structure of a wreck;

ElGURE'dshows a hook. with a, cuttingdevice for. the strings which hold: the, bag in folded. condition;

FIGURE. 7. shows. a crosszesection through a pressure differential valve according tohtheinvention;

FIGURE 8, is, a sectional view along, line VIIL-VIII of FIGURE 7; and

FIGURES 9, and 10 show, typical arrangements of salvage bags at a wreck. Referringnowio, the, drawing, wherein like reference numerals indicate like parts, FIG. 1 shows a salvage bag 1 attached to a bottom 2 and a top 3. The top and bottom constitute, rigid end, members of; the flexible bag. The bottom, is preferably of generally elliptical cro ss section, having aj frusto-conical extension 4, and is stiffened by mutually perpendicular center plates 5 and 6. A padeye 7 is fixed. to the bottom and serves for the attachment of hooks, shackles, and other salvage means. Pressure differential valves 8 (to be described in detail hereinafter) are placed inside top 3. Top 3 has air p nin s .0.. Anv a supp y p p 1 is ed, for instance, at the center of top 3. Within the housing for the pressure differential; valves '8 there is a screen v 12 for preventing debris toenter the orifices of the pressure differential valves, ti. Wing spaces 15 of top 3 are used, for holding suitable gas-evolving chemicals. Special valves 14, preferably electrosmagnetic and remote-controlled, allow'wa'ter. to eriter the space 13 by conduits 15. Top 3 is equipped with pad eyes 16-. The lower side of top 3 carries a ring 17 which engages rim 18 of cone 4 when the salvage bag is folded. Below the wing spaces 1 -3. there are openings 19 through which gases may pass to inflate the bag 1. v

If a certain excess pressure inside bag 1 over the outside water pressure is present, the bag expands over its entire length to a full cylinder with the diameter 2G. in case the inside pressure of the bag is lower than the outside water pressure, the bag 1 has a generally. hyperbolical cross-section, as shown at 21, where the lower portion 22 of bag 1 clings to thegwall of cone 4.

The; bag 1 may have horizontal stained stripes 23 which serve as draft marks for the salvage master for sal vage bags which are used as buoyancy and stability memhe e, t he su f Ringsf'24 clamp bag 1 to the bottom 2 and top 3. The outer sides 25 of the bottom 2 and the top 3 and the inner side 26 of the ring 24 are matchingly corrugated, as shown by. FIG. 2 in connection with top 3. The bag 1 is held between corrugated outside 25 of the top and the bottom, and ring. 24 and'forms the corrugated areas 27 when the screwbolt 28 is tightened to secure split ring 24.; Since the force. of screwbolt 28 transmits a mom nt to ring 24 visits fl nges 29;"se, those arts of rin 24 close to flanges 29, 30- are prevented from a permanent lift by screwbolts 31, 32, mounted in holes 33, 34 which are oval in circumferential direction to assure tightening of ring 24 over the entire circumferential area (see FIG. 3).

As shown in FIG. 4, the salvage bag 1 is kept in folded condition 35 by strings 36. which are laid over pairs of hooks 37, 3S fixed along the circumference of rings 24. Strings 36 are under tension. The'upper hook 38 is equipped with a movable piece 39 which is pressed up.- ward by spring 40 (see FIG. 6). The piece 39 on which the string 36 rests while the salvage bag 1 is in stowed or folded condition 35, has a slot 41 for a razor sharp cross member 42 fixed to the hook 38.

In the absence of any inflation, spring 40 presses the movable piece 39 upwards,'thus counterbalancing the string force, keeping the string well above the sharp cross member 42. As soon as the bag 1 is inflated, the top tends to move away from the bottom and thereby lengthens the elastic strings 36, which maybe of rubber. This will press down the spring 40 and the string is thereby moved against the sharp upper edge of the cross blocks of concrete or billets may be attached to the salvage bag temporarily in order to make it slightly heavier than the water it displaces and thus to produce a slightly underbalanced buoyancy, lugs 43a being provided for this purpose on the top and bottom. The salvage bag having its Weight center below its center of buoyancy will float horizontally while submerged by a rope 44 from a boom of a tender or barge. Since the salvage bag is almost weightless when submerged and floats in such a way that the pad eye 7 is directed to the side, a diver can easily connect the pad eye 7 of the salvage bag 1 to the pad eye 45 of the outrigger 46 which is attached to the hull 47 by hooks 48 or screwbolts 49 (see FIG. 5), preferably on hard points of the hull structure of the wreck to be salvaged.

After the salvage bag 1 has been secured to the outrigger 46, the diver removes the temporary weight 43 which may be connected by a line 48 to the rope 44. At the same time rope 44 is disconnected from the salvage bag 1. Because the salvage bag 1 has surplus buoyancy after removal of the weight 43 it turns around the pad eye 45 of the outrigger 46 in the direction of arrow 49 and keeps steady in this position, as indicated by broken lines 50.

It should be noted that the suggested method of placing the salvage bags at the proper location of the wreck ensures the advantages that, during this preparatory period, there are no air pressure lines connected to any bag and no tangling air pressure lines are present which could mean an obstacle to the diver. No salvage bag is expanded at this period so that the minimum possible profile of the salvage bag only is exposed to currents and tides in contrast to steel cylinders and pontoons which have to be placed below the water with their entire and unchangeable profile and shape. This means in the latter case,- under unfavorable circumstances, a creation of tremendous forces by tides and currents, making the attachment of such huge steel cylinders and pontoons below the water surface at great depths a tedious, dangerous and sometimes an even impossible diver job.

In addition to this grave detriment, there is also the heavy steel weight of steel cylinders or pontoons including the ballast water which in this case has to be considered a frozen weight. r

In contrast to this, asalvage bag is almost weightless under water. There is no ballast water constituting a weight which has to be shifted around during attachment work to the wreck, no matter how large a salvage bag may be. The weight consideration alone demonstrates the superiority of salvage bags over steel pontoons or cylinders as a salvage equipment, not to mention the profile characteristics in regard to presenting large surfaces to attacking currents and tides.

If the weather is unfavorable or tides do not allow raising of the ship, the salvage bags may be left below in their folded condition. When salvage work is started, air pressure lines are connected to the salvage bags and the bags are thereupon inflated.

Referring now to FIG. 7, valve Sis shown as a pressure differential valve comprising a piston 51 downwardly biased by a spring 52. As soon as the pressure in the inside chamber 53 increases above the outside pressure of water 54 beyond a predetermined differential pressure, piston 51 moves upwards, allowing air to escape through the valve body orifices 55 in the direction of arrows 56, 57. A bell 58 forms a space 59 which is occupied by the compressed air escaped from chamber 53 freely communicating through openings 9 with the interior of bag 1. The air in space 59 forms a cushion which prevents water from entering orifices 55 while piston 51 moves up and down. In the closed position of FIG. 7, one or two gasket rings 60 provide air-tightness.

In order to make the air cushion in space 59 eflicient, it is essential that the lower edges of the orifices 55 are arranged high above the lower edge 62 of hell 58.

Ribs 63 support the upper portion of the pressure differential valve and serve also as a guide for piston 51. Ribs 63 are directed radially to streamline the flow of escaping air. Piston 51 abuts noses 64 in the closed position of the valve.

FIGS. 9 and 10 show a wreck 65 resting on the ground 66. Stability and buoyancy bags 67 are attached to said wreck 65 by chains or a. rope system 68 with lead lines 69 to a winch 70 of a salvage barge 71. Buoyancy bags 72 below the water surface 73 are attached to the forward and aft portion of wreck 65.

Square-shaped bags 72a are placed in the midship region of wreck 65 and are equipped with a box-like girder 74 which houses an air supply pipe 75 for supplying compressed air to the separate compartments of the bag 72a which has bulkheads 76, as shown in FIG. 9. Strongbacks 74 and salvage bags 72 are connected by ropes 77 which are led below the bottom 78 from port to starboard side and attached to the outrigger 46.

As will be evident from the above detailed description of certain preferred embodiments of the invention, the flexible and expansible salvage bags act as lifting ropes so that the fabric of the bags is exposed to additional forces in a vertical direction which forces are superposed over the circumferential forces and the constant vertical force created by the resulting inner and outer pressure. With regard to the stress of the fabric of salvage bags, particularly in case of salvage bags having a great overall length, the pressure dilferential valve should be arranged at the top of the salvage bag for the following reason:

The inside pressure at the top of the salvage bag has to correspond with the outside water pressure plus a different al pressure for which the pressure differential valve is set 1n order to expand the bag. The outer water pressure increases linearly from the top to the bottom of the salvage bag. The total difference of the water pressure from the top to the bottom of a salvage bag remains constant at a given height of the bag, notwithstanding in what water depth the bag is placed.

In order to produce full expansion of the bag and, thereby, full buoyancy, the inside pressure of the bag which is uniform all over the bag must be at least equal to the total difference of the outer water pressure from the top to the bottom of the bag. Otherwise a certain lower portion of the bag would be pressed together due to lack of sufiicient inside pressure which means in this case loss of buoyancy.

Therefore at a progressing distance from the top of the salvage bag, the difference between the constant in side pressure and the increasing outside pressure steadily decreases resulting in a linear decrease of the circum: ferential stress of the fabric of the bag in a vertical direction. On the other hand, the buoyancy forces of the bag are integrating from the top to the bottom of the bag where they meet the counterforce at the salvage hook. The combined stress of the fabric of the salvage bag, created by the superposition of the steadily decreasing circumference resultant forces, the steadily increasing vertical (buoyancy) forces and the constant vertical force (due to the constant differential pressure), is ale most constant at any distance from the top, notwithstandv ing the water depth where the salvage bag maybe placed.

A pressure differential valve located at the bottom of the-salvage bagwould require agreater differential pressure, due to greater Water pressure at the bottom than at the top, in order to keep the bag fully inflated for maximum possible buoyancy of the bag. This would result in a greater combined, circumferential and vertical stress of the bag not balanced by the counteracting water pressure which increases from top to bottom. The total superposition of all acting vertical and circumferential forces does not result in a fairly uniform stress of the fabric of the bag when the valve is located at the bottom as it is, the case when the pressure differential valve is arranged atop the salvage bag.

In, order to ensure. economical use of the fabric of a salvage bag having a great length, it is, therefore, from the, viewpoint of uniform stress andfor safe operation, essential that the pressure differential valve be placed atop the salvage bag. Smaller bags may have the pres.- sure differential valve at the bottom if for certain reasons such arrangement should be desirable.

Nylon or a similar polyamide fiber is the preferred material for the bag fabric. The strength of nylon or the like fabric is generally known. In a certain sense, the salvage bags herein described are, in principle, nylon tropes designed to act as pulling means and at the. same time to provide the required pull by expanding them in order to produce buoyancy forces.

When the bag is filled with air or gasv at only loW pressure in the presence of greater water pressure, the lower portion of the bag is compressed by the outer water pressure in such a way that the bag develops a shape, similar to a mushroom in the same way as highaltitude balloons do. before taking off. In this case only a portion of the maximum possible buoyancy of the bag is produced.

These conditions should be observed in an appropriate design of the bottom and the top of salvage bags. As already mentioned, salvage bags, when expanded, produce considerable uplift-forces which serve to raise a Wreck. The bottom of a salvage bag should, therefore, be designed to withstand these great forces. First of all, sharp corners should preferably be avoided, which otherwise could impair the fabric and lessen its strength. A special shaped bottom of a rigid material, for instance, steel, aluminum or the like, is preferably used for the transfer of the forces originating from the bag. As shown in the drawing, the bottom is preferably elliptical. The bag may be glued or otherwise fixed to the top and bottom, the fixing means shown being screws and rings which press the bag in grooves, thus making for tightness and preventing the bag from slipping off. The bottom, at its lower portion, is equipped with a strong pad eye for applying shackles, hooks, ropes or the like means for salvage purposes.

The top of the bag is built basically in the same Way including a pad eye if it should be found desirable to couple salvage bags in vertical or any other direction and to facilitate handling. The top is equipped with one or more pressure differential valves. The valves have to be placed at a safe place, they should be safeguarded against damagefrom possible dislocation of the bag and contacting a. wreck while the salvage bag is inflated, which involves the creation of considerable forces. Therefore, as-amatterof'safety, the pressure differential valves are preferablylocatedinside the top in a special housing.

The shape 0f the1salvage bags is preferably cylindrical] with eferably hemi sphericalor half-elliptical ends; Gomp rely sphericalbagsmay also be used. In some casesfitis desirable to use bags of a square-like crosssection with, preferably hemispherical tops and ends; Suchpo-lygonal salyage bags may be sub-divided by bulkheads, of the same foldable material, in a number of compartments, eaph compartment tob e equipped with one or more pressure difierential-valyesratop or at, the bottom. The bot-tom anchorage, the cross-section of which is shaped basicallyin the sameway asdescribed above, may e iu tasa irde th nr r p y tube: h box girder serves simultaneously as a strong-back with a number of pad eyes for, hooks, shackles and other salvagemeans,

The bottom cone 4 serves a dual purpose. First, the top of thesalvage bag isbrought up to the cone whereby the, lower side of the top equippedv with a ring of small height, engagestheupper edge of thecone attached to the bottom, In this way top and bottom are centered and ke t a th desir is anc n t wa io -r ondly, thesp'ace between the cone and the outside diameter of, the topandthe bottom serves as a stowage space for the bagin foldedconditiom Vertical strings 3 6 distributedaround the circumference of the top and bottom hold top andbott-om together and guard the folded bag inside the stow-age space between topandbottom.

Strings 36 may be of rubber. band and laid around hooks. The stringsaround. thecircumference ofthe top and bo ttomkeepboth, the top and the bottom, firmly together at the distance of the c one. This facilitates the attachment of the bag to the Wreck, particularly when Weightand displacement of the salvage bag are balanced. The bag is preferably submerged in the above described folded condition by applying a hook attached to a point of the circumference of the salvage bag and to distribute the weight of the salvage bag in such away that the salvage bag has a small underbalanced buoyancy and when. submerged hangs on the rope vertically with a horizontal axis. A body with an underbalanced buoyancy, has a weight greater than the weight of the water itdisplaces, i.e. it sinks in water. Thisis in contrast to a, balanced buoyancy exhibited by a floating ship, for

instance, the weight of which equals theweight of the dis-' placed water. A salvage bag with a small underbalanced buoyancy, i.e. theweight of which is slightly in excess of the displaced water, enables the diver to attach the pad eye to the wreck or other appliances easily.

Outriggers, such as tripods, are preferably attached to the wrecks lower side approximately at the height of the double bottom, by screws, welds, or ropes which also may be led around the bottom of the wreck from one side to the other, connecting two opposite Outriggers on port and starboar-dside. The lever arm of the Outriggers should be somewhat larger than the radius of the salvage bag in order to keep the salvage bag, when inflated, clear of the ships side. In case the hull is covered with sharp shells, a tarpaulin or other cover should be provided in order to prevent chafing of the salvage bag.

Outriggers should be built from pipes and be of neu tral buoyancy for easy handling when submerged and when placing them at the desired location of the wreck. Outriggers and salvage bags, the latter in folded condition, may be connected prior to lowering and then submerged as one unit. The entire unit should have a small underbalanced buoyancy.

Other salvage bags, which are at a higher location at the wreck, do not require outriggers. They may be attached to the wreck by ropes and shackles at strong points of the hull, for example, bulkheads, hatchend beams, or the like structures.

The orifices of the valve have to be designed of ample size in order to allow a suflicient escape of air or gas and to prevent an undue increase of the inside pressure of the salvage bag, due to insufficient air escape areas. This is of particular importance when the salvage bag ascends with comparatively high velocity, resulting in a rapid decrease of the water pressure. If the relief of the inner pressure of the salvage bag is not able to follow a rapid decrease of the outer water pressure, the fabric of the salvage bag may be overstressed, resulting in a breakdown of the salvage bag and loss of buoyancy, thus possibly endangering the entire force system of the salvage operation.

Large orifices of the pressure differential valve, on the other hand, may allow water to enter the salvage bag if no special precautions are provided.

Entering of water into the Salvage bag through the pressure differential valve has to be avoided under all circumstances while the valve opens and closes during ascending of the salvage bag. Therefore, a bell is preferably provided around the orifices of the pressure differential valve in such a way that the lower edge of the bell is at a substantially lower level than the lower level of the orifices. As soon as air or gas escapes, water surrounding the orifices will be pressed out of the space between the orifices and the bell and will be pressed down to the lower level of the bell. When the valve closes, no water can reach the orifices because of the compressed air cushion which now occupies the space between the orifices and the bell.

The gas developing chemicals are preferably placed in more than one chamber for the following reason:

A wreck may rise quickly after it comes free from the ground. The stability bags thereby lose buoyancy and the ship descends again. The lower salvage bags which had been inflated by gas developing chemicals have meanwhile blown off a certain amount of gas while the wreck was first rising. After sinking down again, the salvage bags are compressed due to lack of sufficient inside pressure at the greater water depths. The loss of buoyancy has to be made up while initiating the second phase of raising the ship by applying a second or third chamber of chemicals.

If the wreck is not subject to special retention forces, which are suddenly released while lifting forces act on the wreck and stability of the system is not a problem, the salvage bags need not reach the water surface in order to establish a waterplane inertia. In this case, the salvage bags merely need to be attached to the wreck and, after that, inflated.

Salvage bags along the wreck have to be arranged in such a way that the buoyancy forces created by the expansion of the salvage bags prevent tilting or other undesirable dislocations of the wreck while it is raised. The buoyancy of each salvage bag can be varied as to requirements by either increased compressed air supply which means an increase of lifting forces or by reducing air compression which reduces the lifting forces. This procedure results in a sensitive adjustment of required lifting forces of the entire system.

In case retention forces are present, for example, due to mud in which the wreck is embedded, precautionary measures should be provided so that the wreck will not rise quickly in an uncontrollable manner after the retention forces are released, leaving the buoyancy forces of the salvage bags with a corresponding free lifting force. In order to cope with this situation, the salvage bags are used as follows:

In addition to those salvage bags attached to the wreck in submerged condition with no inertia of waterplane, additional salvage bags are connected to the wreck by chains or ropes, preferably two on port and starboard side each and towards the end of the wreck. These additional salvage bags extend partly over the surface of the water where they act as stability members of the system. These upper salvage bags are inflated first, exerting a lifting force on the wreck. If the lifting force is not capable of moving the wreck, the lower bags are then inflated slowly up to that point where the wreck comes free from the ground or mud. The sudden freeing of the retention forces tends to move the wreck upwards in a more or less violent motion, however, under full control of the stability due to the upper salvage bags. While the wreck rises upwards in the described manner, the upper bags rise in the same way, losing thereby buoyancy and, in consequence of this, the upper salvage bags lose a certain amount of lifting force which slows down the upward motion. The upper salvage bags thus act as a break.

The wreck may sink again up to the point of equilibrium between its submerged weight, the total lifting forces of all salvage bags, and, if the wreck should again touch the ground, any retention forces created thereby. In this case, the lower bags are further inflated, which brings the wreck to the surface.

Meanwhile the upper salvage bags have emerged fully out of the water and do no more contribute to the floating stability of the system.

To keep upright full control of the stability throughout the draising operation, two different methods may be app 1e After the first period of applying lifting forces, i.e., up to the point where the retention forces are released, the ropes or chains of the upper salvage bags may be short ened at the rate of the wrecks rising to keep them afloat with an inertia of waterplane and to use them further as lifting forces producing buoyancy bodies.

The second method provides ropes attached to the wreck and to salvage barges whereby the ropes are hauled while the wreck is raised 'by the lower salvage bags. In this case, the upper bags are removed when the retention force has been released and, after the ropes are tight, the salvage barge takes care of the floating stability of the system.

Both methods may be combined in that the upper salvage bags remain in their places and are attached by a number of sheaves and blocks to a rope system, the leading lines of this system being connected to winches on board a salvage barge.

If it is required to tow a raised wreck hanging on the salvage 'bags at a smaller draft or to raise the deck of :the wreck a certain distance above the water level, buoyancy bodies are preferably provided below the bottom, said buoyancy bodies consisting of a number of cylindrical or square-shaped inflatable bags. Such bags intended to serve as additional buoyancy bodies when the ship is already raised or used in case of emergency with a damaged ship, do not require pressure differential valves but pad eyes on both ends and air supply sockets. They may easily be pulled below the bottom in folded condition similar to collision mats and, after proper attachment, are inflated to produce the required additional buoyancy.

Chemically and air inflated salvage bags may be used in combination, which offers the following advantages. Chemically inflated salvage bags should be arranged at the lower side or bottom of a wreck. Their lifting capacity shouldlae less than the total required lifting buoyancy. The r'emaining required buoyancy should be produced by controllable and adjustable air pressure salvage bags, the latter preferably located towards the end of the ship and serving also as stability control members.

'Such combined operation of salvage bags, some of them expanded by air pressure from outside and others expanded independently from other sources, keeps the entire salvage operation under control as to required buoyancy, trim conditions and the like and cuts down the otherwise required numerous underwater air pressure 9 lines from a salvage barge or a salvage airplane to the bags.

The technical and economical advantages of the device as herein described consist in a light :and comparably inexpensive equipment which easily can be stowed, transported and handled; Therefore, only a small salvage tender or barge. equipment. with. air compressor units is required even. for largestsalvage operations. The displacement of -a salvage barge no longer makes any difference. A small tender means less operation costs and contributes to a substantial cut-down of salvage costs, furthermore shortening the salvage time materially. .Salv-age bags may be transported by airplanes to the spot of emergency within the shortest time possible. While the salvage tender moves -to the scene, salvage bags meanwhile :are attached .to the wreck. Upon arrival of the tender with air compressor units, they are ready to be inflated. There is no cumbersome, expensive, and time consuming towing or transporting of -a large number of heavy steel salvage drums or pontoons up to 5,000 tons displacement.

Salvage bags :allow a sensitive adjustment of lifting forces by merely changing the air pressure. In contrast to rope operations via winches, lifting forces applied to a wreck are thus controllable and exactly known. In this way accidents and unforeseen situations can be avoided. A salvage operation using salvage bags in accordance with the present invention establishes a statically determined system with all its advantages whereas ropeoperated salvage work is basically statically undetermined with all its disadvantages, for example, overstressing of certain ropes which, when breaking, can upset the entire salvage operation with accidents to men and loss of expensive equipment. Salvage bags in accordance with the present invention may also be applied for submersible platforms, foundations and like structures in order to drop or remove such structures which lack buoyancy or stability or both.

Known gas evolving agents may be use-d for inflating the bags. Such agents are, for instance, calcium carbide which develops acetylene with water, metal hydrides, such as lithium hydride, sodium hydride, lithium aluminum hydride, lithium borohydride, calcium hydride, or metal nitrides such as magnesium nitride which yield hydrogen or, respectively, nitrogen on contact with water, metal peroxides such as sodium peroxide, which are decomposed by water to oxygen, metals, such as activated magnesium or aluminum, and others.

I claim:

1. A maritime salvage device for raising a salvage objeot, comprising an inflatable bag of a tubular foldable sheet material, a rigid top and bottom member at each end of said tubular sheet material, means for air-tightly afiixing the ends of said tubular sheet material to respective ones of said rigid members, a substantially frustoconical element extending inwardly from one of said rigid members, means for centering the rigid members when the conical element is in contact with the other rigid member, said element and the members defining a storage chamber for the folded sheet material, an elastic tie means for holding the rigid members together when the bag is not inflated, a plurality of longitudinally aligned pairs of hooks fixed respectively to the top and bottom members, cutting means mounted in at least one hook of each of said pairs of hooks, each cutting means comprising a stationary cutter extending across the hook, a slidable element in each hook and having a slot engaging the cutter, and biasing means for normally holding the slidableelement above the cutter, the tie means engaging the slida-ble elements in said hooks and being strung over each of said pairs of hooks.

2. The maritime salvage device of claim 1, further comprising means mounted in at least one of said rigid members for supplying a gaseous medium to the interior 10 of the bag, said rigid member defining :aplural-ity of chambers for, holding said means.

3;. A maritime salvage device for raising a salvage object submerged in water, comprising abuoyancy body constituted by :a single-walled bag of a fol-da ble sheet material; a gaseous medium in the interior ofsaid bag for, effecting a desired" buoyancy ofv the. bag when immessed in water; a pressure differential Valve withinsaid bag, said valve including a cylindrical valve seat, means responsive to a set pressure differential between the pressure of the gaseous medium in the interior 'of the bag and the pressure of the water outside the bag, the pressure difierential responsive means being mounted in the valve seat and opening relatively large orifices in said valve seat when the set pressure differential is reached and thus permitting gaseous medium to escape from the interior of the bag, a bell-shaped element surrounding said orifices and extending with its lower edge substantially below the orifices to define a sealing air cushion chamber between the lower portion of the bell-shaped element and the orifices while submerged, and a plurality of radial rib-s connecting the valve seat and the bell-shaped element; and means for attaching the bag to the salvage object.

4. The maritime salvage device of claim 3, wherein said bag is constituted by a tubular foldable sheet material and convexly curved rigid top and bottom members, means being provided for aflixing the respective ends of said tubular sheet material 'airtightly to said members, means mounted in at least one of said rigid members for supplying the gaseous medium to the interior of the bag, said gaseous medium supply means including said pressure differential valve, and said salvage object attaching means being afiixed to at least one of said rig-id members.

5. The maritime salvage device of claim 4, wherein each of said rigid members constitutes a housing, said gaseous medium supply means being mounted in the housing constituted by the top member, and a frusto-conical elementinwardly extending from the housing constituted by the bottom member inside the tubular folda-ble sheet material.

6. The maritime salvage device of claim 4, wherein said gaseous medium supply means comprises a storage means in said top member and a chemical substance stored in said mean-s, which evolves gases upon contact with water.

7. A maritime salvage device comprising a substantially V-shaped outrigger, means for attaching a salvage object submerged in water to said outrigger, a pad having at least one hole mounted on the apex of said outrigger,

and at least one buoyancy body attached to at least one of said pad holes, the outrigger having a balanced weight as to buoyancy and displacement, when Submerged in the water.

8. The maritime salvage device of claim 7, wherein said outrigger is constituted by a tripod of pipes.

References Cited in the file of this patent UNITED STATES PATENTS 387,933 Travis Aug. 14, 1888 923,801 Bargar June 8, 1909 1,002,184 Serres Aug. 29, 1911 1,009,123 Williamson Nov. 21, 1911 1,301,515 Smith Apr. 22, 1919 1,416,754 Reno May 23, 1922 1,486,131 Dutton Mar. 11, 1924' 1,554,316 Winship Sept. 22, 1925 2,058,708 Minio Oct. 27, 1936 2,213,375 Barna Sept. 3, 1940 2,225,880 Montelius Dec. 24, 1940 2,243,711 Lamb May 27, 1941 2,313,215 Bierlee Mar. 9, 1943 (Other references on following page) 11 UNITED STATES PATENTS Winkler Mar. 20, 1945 Ming Apr. 24, 1945 Cook Dec. 10, 1946 Cook Dec. 31, 1946 Rinnie May 23, 1950 Davison May 12, 1959 Pedrowich May 19, 1959 12 Ralleo et a1 June 30, 1959 Gibbons Oct. 27, 1959 Green Now. 10, 1959 Cunningham May 31, 1960 FOREIGN PATENTS France Feb. 13, 1904 Great Britain June 30, 1921 

1. A MARITIME SALVAGE DEVICE FOR RAISING A SALVAGE OBJECT, COMPRISING AN INFLATABLE BAG OF A TUBULAR FOLDABLE SHEET MATERIAL, A RIGID TOP AND BOTTOM MEMBER AT EACH END OF SAID TUBULAR SHEET MATERIAL, MEANS FOR AIR-TIGHTLY AFFIXING THE ENDS OF SAID TUBULAR SHEET MATERIAL TO RESPECTIVE ONES OF SAID RIGID MEMBERS, A SUBSTANTIALLY FRUSTOCONICAL ELEMENT EXTENDING INWARDLY FROM ONE OF SAID RIGID MEMBERS, MEANS FOR CENTERING THE RIGID MEMBERS WHEN THE CONICAL ELEMENT IS IN CONTACT WITH THE OTHER RIGID MEMBER, SAID ELEMENT AND THE MEMBERS DEFINING A STORAGE CHAMBER FOR THE FOLDED SHEET MATERIAL, AN ELASTIC TIE MEANS FOR HOLDING THE RIGID MEMBERS TOGETHER WHEN THE BAG IS NOT INFLATED, A PLURALITY OF LONGITUDINALLY ALIGNED PAIRS OF HOOKS FIXED RESPECTIVELY TO THE TOP AND BOTTOM MEMBERS, CUTTING MEANS MOUNTED IN AT LEAST ONE HOOK OF EACH 